Indicators, Acids, and Alkalis Flashcards
What is an indicator?
An indicator is just something that changes colour depending on whether it’s in an acid or in an alkali.
What is litmus paper?
Litmus paper is quite a popular indicator, but it only tells us whether a liquid is an acid or an alkali - it does not say how strong it is. Acids turn litmus paper red and alkalis turn it blue.
What is universal indicator?
Universal indicator solution is a very useful mixture of dyes which gives the colours shown in a pH chart.
How can you make red cabbage indicator?
1) Stir some cut leaves of red cabbage in a beaker of boiling water to obtain a red solution.
2) Filter the solution to remove all salts.
3) Add to acid or alkali.
It will turn pink/red if it is an acid, and it will turn green/yellow if it is an alkali.
What does the pH scale show?
The pH scale shows the strength of acids and alkalis. The pH scale goes from 0 to 14. pH can also be shown by colour universal indicator turns.
What is the pH of an acid?
Anything with a pH below 7 is an acid and will turn universal indicator red, orange or yellow.
What is the pH of the strongest acids?
The strongest acids have a pH of 0.
What is the pH of an alkali?
Anything with a pH above 7 is an alkali and will turn universal indicator blue or purple.
What is the pH of the strongest alkalis?
The strongest alkalis have a pH of 14.
What is the pH of a neutral substance?
A neutral substance (e.g. pure water) has a pH of 7 and will turn universal indicator green.
What do acids and alkalis do to each other?
Acids and Alkalis neutralise each other.
What is formed when acids react with alkalis?
Acids react with alkalis to form a neutral solution of a salt and water.
What is the word equation for neutralisation?
acid + alkali ==> salt + water
Why is it known as a neutralisation reaction?
This is known as a neutralisation reaction because the products have a neutral pH (a pH of 7).
What are everyday uses of neutralisation?
Treating indigestion or using toothpaste
